Header for a heat exchanger

A header for a heat exchanger for a charge air cooler, comprising:

• an opening plane with a plurality of openings for attachment of tubes;
• a collar encircling the perimeter of the opening plane and protruding at least partially above the opening plane;
• and
• guiding protrusions comprising a first group of guiding protrusions and a second group of guiding protrusions, the plurality of guiding protrusions being located along an inner perimeter of the collar adjacent to said openings and configured to guide the tubes into the openings upon insertion,
• wherein the openings have rectangular shape with longer sides and shorter sides and are arranged in series along their longer sides,
• wherein the first group of guiding protrusions is located adjacent the longer sides of the openings, while the second group of guiding protrusions is located adjacent the shorter sides of the openings,
• wherein the collar has a rounded inside collar edge, the openings have rounded inside opening edges, and each guiding protrusion forms a flat surface which connects tangentially with the inside collar edge and a respective adjacent inside opening edge.